Altered compartimentalization of transforming growth factor‐β in asthmatic airways

Abstract

Summary Background Asthma is characterized by alterations of the bronchial epithelium associated with inflammatory cell infiltrates and sub‐epithelial fibrosis. Transforming Growth Factor‐β (TGF‐β) is an anti‐inflammatory and fibrosing cytokine normally present in bronchial epithelial cells and also potentially produced by inflammatory cells. Thus, TGF‐β could play a role in the asthmatic process, and its expression could be modified in asthmatic airways. Objective To test this latter hypothesis, we studied the bronchial distribution of TGF‐β in asthmatic patients. Methods TGF‐β1, 2, 3 distribution was studied by immunohistochemistry in bronchial biopsies from 12 asthmatic patients and 10 non‐asthmatic subjects. Results Bronchial epithelial cells from asthmatics were negative or faintly positive while a bright staining was detected in these from non‐asthmatics ( P < 0.0l). In both groups, when inflammatory cells were present beneath the basement membrane, they were stained by the anti‐TGF‐β antibody. Conclusion This study shows an altered compartimentalization of TGF‐β in asthma. (a) TGF‐β is scarse in asthmatic bronchial epithelial cells, which could favour the perennization of the bronchial inflammation, and (b) TGF‐β is present in inflammatory cells beneath the basement membrane, where it could be involved in the frequent sub‐epithelial fibrosis.